POST-SPRINT TRAINING ESSENTIAL AMINO ACID INGESTION ALTERS MUSCLE PROTEIN SYNTHESIS
Rundqvist, H. C., Esbjornsson, M., Rooyackers, O., William, A., Moberg, M., Osterlund, T., & Jansson, E. (2016). Amino acid transport after sprint exercise and oral amino acids. Medicine & Science in Sports & Exercise, 48(5), Supplement abstract number 90.
This study assessed if oral ingestion of essential amino acids increases the amino acid transporter SNAT2, Akt/mTOR signaling, and muscle protein synthesis after sprint exercise. Ss (N = 12) performed three 30-s sprints separated by 20 minutes of rest. Ss consumed essential amino acids + maltodextrin solution or flavored water (placebo) during the sprint exercise up to 15 minutes after the last sprint in a randomized order with a one-month interval. In vivo muscle protein synthesis rate was measured using a stable isotope technique. Ss received a stable isotope of phenylalanine (D5-phenylalanine) to label the precursor pool for protein synthesis. Continuous infusion started before the first sprint and ended 200 minutes after the last sprint. Two post-exercise biopsies (vastus lateralis) were obtained 80 and 200 minutes after the last sprint. The amount of labeled phenylalanine incorporated into muscle protein over the two hours represents the in vivo muscle protein synthesis rate and was expressed as fractional synthesis rate (FSR %) calculated by dividing the amount of labeled phenylalanine incorporated during the two hours by the amount in the free amino acid (precursor) plasma pool. Biopsies were also analyzed for Akt/mTOR signaling and SNAT2 amino acid transporter by Western blot and for SNAT2 gene expression by real-time PCR. Blood samples were analyzed for amino acids, glucose, lactate, and insulin. Four Ss, involuntary vomited after exercise during the essential amino acids condition and showed a minor increase in plasma leucine. Their analyses were presented separately.
For non-vomiting Ss (N = 8), the expression of the amino acid transporter SNAT2 was higher both at the protein and the mRNA level after essential amino acids ingestion after placebo. Fold increase for phosphorylated Akt, mTOR and p70 was 1.7-3.6 comparing essential amino acids to the placebo. FSR % after essential amino acids was increased by 25% compared to placebo. None of those variables were significantly increased in the Ss who vomited.
Implication. Oral essential amino acids increased muscle protein synthesis after sprint exercise. Enhanced capacity for amino acid transport and subsequent enhanced Akt/mTOR signaling were suggested to mediate the increased muscle protein synthesis. This study did not evaluate any performance factor or measure and while it showed a post-exercise change, the role of that change for recovery was not determined.
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